An experimental study into the effect of the pilot injection timing on the performance and emissions of a high-speed common-rail dual-fuel engine

Abstract

Dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. In these smaller-capacity high-speed engines, where the combustion event can be temporally shorter, the injection timing can have an important effect on the performance and emissions characteristics of the engine. This paper discusses the use of a 0.51 l single-cylinder high-speed direct-injection diesel engine modified to achieve port directed gas injection. The effect of the pilot diesel injection timing on the dual-fuel engine performance and emissions was investigated at engine speeds of 1500 r/min and 2500 r/min and loads equivalent to gross indicated mean effective pressures of 0.15 MPa, 0.3 MPa, 0.45 MPa and 0.6 MPa, for a fixed gas substitution ratio (on an energy basis) of 50%. Furthermore, the effect of the pilot injection quantity was investigated at a constant engine speed of 1500 r/min by completing a gaseous substitution sweep at the optimised injection timing for each load condition. The results identify the limits of single-injection timing during dual-fuel combustion and the gains in the engine performance and stability that can be achieved through optimisation of the pilot injection timing. Furthermore, the pilot injection timing and quantity were shown to have fundamental effects on the formation and emissions of carbon monoxide, nitrogen oxide and total hydrocarbon. The potential for dual-fuel combustion to achieve significant reductions in the specific carbon dioxide was also highlighted, with reductions of up to 30% being achieved at full load compared with the baseline diesel case.